docs: def params(self_, parameter_name=None):
          """
          Return the Parameters of this class as the
          dictionary {name: parameter_object}
  
          Includes Parameters from this class and its
          superclasses.
          """
          if self_.self is not None and self_.self._instance__params:
              self_.warning('The Parameterized instance has instance '
                            'parameters created using new-style param '
                            'APIs, which are incompatible with .params. '
                            'Use the new more explicit APIs on the '
                            '.param accessor to query parameter instances.'
                            'To query all parameter instances use '
                            '.param.objects with the option to return '
                            'either class or instance parameter objects. '
                            'Alternatively use .param[name] indexing to '
                            'access a specific parameter object by name.')
  
          pdict = self_.objects(instance='existing')
          if parameter_name is None:
              return pdict
          else:
              return pdict[parameter_name]